Redundant sensor system for common mode failure avoidance
A redundant sensor system includes first and second sensors of the same type. The first and second sensors are configured to sense and measure a parameter, such as torque, applied to an object, such as a shaft. A preselected measurement value difference is provided between the first and second sensors. The preselected measurement value difference, such as an offset or a difference in sensor gain, can be utilized by the redundant sensor system or an associated control system to detect a failure of one of the sensors. Output signals of the first and second signals that do not reflect the preselected measurement value difference within given tolerance indicate that one of the sensors has failed, and a determination that an associated system is untrustworthy can be obtained.
1 . A redundant sensor system for sensing and measuring a torque associated with a shaft, the redundant sensor system comprising:
a first magnetoelastic sensor including a first magneto-elastically active region having first and second axially distinct oppositely polarized magnetically conditioned sub-regions formed by or affixed to a first section of the shaft and a first fluxgate magnetometer pair associated with the first and second sub-regions, the first sensor being configured to sense and measure a first torsional stress induced by the torque at the first section of the shaft, the first section being hollow and having a first inner diameter, wherein the first sensor is configured to output a signal indicative of the first torsional stress;
a second magnetoelastic sensor including a second magneto-elastically active region having third and fourth axially distinct oppositely polarized magnetically conditioned sub-regions formed by or affixed to a second section of the shaft a second fluxgate magnetometer pair associated with the third and fourth sub-regions, the second sensor being and configured to sense and measure a second torsional stress induced by the torque at the second section of the shaft, the second section being hollow and having second inner diameter different than the first inner diameter, wherein the second sensor is configured to output a signal indicative of second torsional stress;
a third fluxgate magnetometer pair associated the first and fourth sub-regions; and
a fourth fluxgate magnetometer pair associated with the second and third sub-regions,
wherein a configuration of the shaft is such that the first and second torsional stresses are different for a given non-zero torque value.
2 . The redundant sensor system of claim 1 , further comprising control circuitry connected in communication with the first sensor and the second sensor, wherein the control circuitry is configured to determine failure of one of the first and second sensors based on signal output of the first and second sensors.
3 . The redundant sensor system of claim 2 , wherein the control circuitry is configured to:
receive the signal output of the first sensor and the signal output of the second sensor; and
calculate the difference in measurement value between the signal output of the first sensor and the signal output of the second sensors.
4 . The redundant sensor system of claim 3 , wherein the control circuitry is further configured to compare the difference in measurement value calculated to the preselected measurement value function, and to output a signal that indicates one of the first and second sensors has a failed state based on said comparison.
5 . The redundant sensor system of claim 1 , wherein the first section of the shaft has a different outer diameter than the second section of the shaft.
6 . The redundant sensor system of claim 1 , wherein an outer diameter of the first section of the shaft is equal to an outer diameter of the second section of the shaft.
7 . The redundant sensor system of claim 1 , wherein the first and fourth sub-regions are oppositely polarized relative to each other.
8 . The redundant sensor system of claim 1 , wherein the first section of the shaft has a first cross-sectional area different than a second cross-sectional area of the second section of the shaft.
9 . The redundant sensor system of claim 1 , wherein the magnetically conditioned sub-regions are selected from the group consisting of bands, strips, rings, and collars, the magnetically conditioned sub-regions being affixed to the shaft.
10 . The redundant sensor system of claim 1 , wherein the third fluxgate magnetometer is configured to output a signal indicative of a magnetic flux induced in the first and fourth sub-regions.
11 . The redundant sensor system of claim 10 , wherein the fourth fluxgate magnetometer is configured to output a signal indicative of a magnetic flux induced in the second and third sub-regions.